Generally, multi-gated non-planar CMOS technology includes metal-oxide semiconductor transistors having a buried oxide layer (BOX) layer formed on a substrate, e.g., a buried oxide layer in a semiconductor-on-insulator substrate. A gate stack, typically of metal and/or polysilicon, is formed on the BOX layer to form the transistor, itself. The gate stack can also include a nitride cap. A high-k dielectric material is blanket deposited on the BOX and the transistor, prior to the deposition of the gate conductor and further processes to complete the transistor.
The BOX layer, however, is susceptible to oxygen diffusion which can negatively affect the performance of the device. That is, outdiffusing oxygen into the high-k dielectric can have many deleterious affects on the performance of the device. For example, the outdiffusion of oxygen into the high-k dielectric can cause growth of extra oxide at the interface of the high-k dielectric and the semiconductor substrate. This, in turn, can result in an increase in equivalent oxide thickness (EOT) and Vt variation. More specifically, the outdiffusion of oxygen can change the work function of the device and hence cause Vt shift. Also, it is known that oxygen can lower the k-value of the high-k material. This, in turn, can negatively affect the device performance.
Accordingly, there exists a need in the art to overcome the deficiencies and limitations described hereinabove.